1. Field of the Invention
The present invention relates to a support for an imaging material, more specifically to a support whose surface on one side of a paper substrate composed mainly of a natural pulp where an image-forming layer is to be formed is coated with a resin sheet, which support not only can provide an imaging material and a print thereon having a high visual gloss and being free of non-uniformity in gloss, particularly silver halide photographic paper and a print thereon (silver halide photographic paper print will be sometimes abbreviated as xe2x80x9cphotographic printxe2x80x9d hereinafter), but also is improved in the property of peeling from a cooling roll used when the support is produced so that no non-uniformity in peeling occurs, and further, which support has excellent curl resistance and an excellent stiffness and can be stably produced at a high speed.
2. Explanation of Related Art
Generally, an imaging material is constituted of a support for the imaging material and an image-forming layer provided on the support. For example, a silver halide photographic material, an inkjet recording material, a thermal diffusion transfer type heat transfer record receiving material, a heat-sensitive recording material or a photosensitive-thermosensitive recording material is produced by forming an image-forming layer such as a silver halide photograph constituting layer, an ink receiving layer, a thermal transfer type heat transfer record receiving layer, a heat-sensitive color-forming layer or a photosensitive-thermosensitive color-forming layer on a support for an imaging material, respectively, and optionally forming an undercoat layer, a protective layer, and the like. In particular, a silver halide photograph constituting layer is constituted of a silver halide photograph emulsion layer, a protective layer, an undercoat layer, either an intermediate layer or a color mixing prevention layer, either a halation prevention layer or a filter layer and an ultraviolet absorbent layer, or a combination of some of these. For example, a simple silver halide photographic material is structured by forming a silver halide emulsion layer and its protective layer on a support for a photographic material. Further, a multi-layered silver halide color photographic material is structured by consecutively forming silver halide color photograph constituting layers such as an under coat layer, a blue-sensitive silver halide emulsion layer and an intermediate layer, a green-sensitive silver halide emulsion layer and an ultraviolet absorbent layer, and a speed-sensitive silver halide emulsion layer and a protective layer, and the like on a support for a photographic material.
There is conventionally well known a resin-coated paper support in which the surface of a base paper for a support for an imaging material is coated with a resin having film formability. Concerning a support for a photographic material for use in a silver halide photographic material, for example, there is known a support for a photographic material in which a base paper is coated with a resin having film formability, preferably a polyolefin resin. There is also known a support for a photographic material in which both surfaces of a base paper are coated with a polyolefin resin. Further, after the application of the rapid photographic development treatment method of a silver halide photographic material, a support for a photographic material in which the both surfaces of a base paper are coated with a polyethylene resin is mainly practically used as a photographic paper, and the resin layer on one side where an image-forming layer is formed generally contains a titanium dioxide pigment for imparting sharpness as required.
Further, there is known a thermal transfer record receiving element having, as a support, a resin-coated paper of which the resin coating has a surface roughness of 7.5 microinches-AA or less, particularly, a polyethylene-resin-coated paper of which the base paper is surface-coated with a polyethylene resin. There is also known an inkjet recording sheet having a resin-coated paper as a support.
However, a resin-coated paper type support for an imaging material, i.e., a support which is formed of a base paper, particularly a base paper composed mainly of a natural pulp, and which is surface-coated with a resin layer on a surface side where an image-forming layer is to be formed, still has several serious problems, and actually, no satisfactory achievement has been obtained.
First, in a resin-coated paper for use as a support for an imaging material, a base paper is coated with a resin having at least film formability, particularly a resin layer containing a polyethylene-based resin, on a surface side where an image-forming layer is to be formed (a surface on which an image-forming layer is to be formed will be sometimes abbreviated as a front surface, a resin layer coating on the front surface will be sometimes abbreviated as a front resin layer, a side opposite thereto will be sometimes abbreviated as a reverse side, and a resin layer formed on the reverse surface will be sometimes abbreviated as a reverse resin layer). The above resin-coated paper is obtained by a series of steps of casting onto a running base paper a film of polyethylene resin composition extruded through a slit die of a melting extruder; pressing them in a nip of a pressing roll and a cooling roll to bond them; cooling the resultant laminate; and then peeling it from the roll. In this case, for producing a resin-coated paper for an imaging material for glossy use, there is used a cooling roll which has a mirror surface, a gloss surface or a finely roughened surface and has an excellent smoothness. In this manner, the front resin layer in a molten state is brought into contact with the cooling roll having an excellent smoothness under pressure. Therefore, the front resin layer could be processed so as to have a surface having an excellent smoothness, and an imaging material using the above resin-coated paper as a support and a print thereon could have a visually high gloss. However, concerning an imaging material using an actually produced resin-coated paper as a support and a print thereon, it has not been possible to obtain any product having a high-gloss appearance. Concerning a photographic paper using a resin-coated paper in particular, it has not been possible to obtain a photographic paper and a print thereon having a sufficiently high-gloss appearance.
The present inventors have therefore made studies for factors of the high-gloss appearance of imaging materials and their prints. As a result, the gloss appearance is affected by various factors such as a resin-coated paper as a support, an image-forming layer and an image-forming method such as development, while it has been found that the gloss appearance is also greatly affected by the factor of a resin-coated paper as a support. The present inventors have therefore made studies on the factor of a resin-coated paper which affects the appearance of gloss. As a result, it has been found that the gloss appearance not only depends upon the factor of a resin layer but also depends upon a variety of factors including factors of the kind and properties of a base paper composed mainly of a natural pulp such as the kind of a natural pulp and a fiber length, conditions of a paper material slurry such as additives for paper, contained in a paper material slurry, paper-making conditions such as a paper-making speed, a bulk density increasing press conditions and machine calender conditions, post-treatment conditions such as size press and tub size press, and further, the surface roughness of a base paper. It has been also found that as the thickness of a front resin layer of a resin-coated paper decreases, the gloss appearance of an imaging material using the above resin-coated paper as a support and a print thereon decreases, and that when the above thickness is 31 xcexcm or less, the above gloss appearance greatly decreases. A photographic material for glossy use is required to give a print having a high gloss appearance, and the problem is that a photographic material which gives a photographic print having a poor gloss appearance is absolutely not suitable for glossy use and has no commercial value.
Second, a resin-coated paper for an imaging material for glossy use is required to have high smoothness. When a base paper is coated with a molten resin by extrusion, however, as the thickness of a front resin layer increases, in particular, when the above thickness is 20 xcexcm or greater or as the speed of production of the resin-coated paper increases, in particular, when the above speed is 200 m/mn or greater, the peeling of the resin-coated paper from a cooling roll is degraded, and a non-uniformity in the form of a lateral height difference in a width direction, called xe2x80x9cpeel non-uniformityxe2x80x9d, occurs on the resin-coated paper. When the above peel non-uniformity occurs, an imaging material using the resin-coated paper as a support and a print thereon cause gloss non-uniformity. The problem is that the gloss appearance further deteriorates and that the commercial value thereof extremely decreases.
Conventionally, there are some methods proposed for overcoming the above problems and some other problems of a support of a resin-coated paper type for an imaging material. For example, there is known a method in which crater-shaped pores which are liable to occur in the front resin layer surface of a photographic support of a resin-coated paper type are prevented or overcome by double layer extrusion coating method by means of co-extrusion coating or consecutive extrusion coating, to provide a photographic support which is free of surface defects and is excellent in smoothness. However, the above method is insufficient for overcoming the above-explained problems, and in particular, it is absolutely insufficient for improving the gloss appearance of an imaging material using a resin-coated paper as a support and a print thereon.
On the other hand, for improving a resin-coated paper in smoothness, there are known methods using a specific pulp such as a pulp having a specific fiber length distribution, a pulp having specific fiber length, width and thickness, a specific conifer pulp or a specific low-density pulp, a base paper having a specific physical property value such as a base paper having a Beck smoothness equivalent to, or greater than, a specific value or a base paper having a surface roughness equivalent to, or smaller than, a specific value. For the same purpose, there is known a method of hot calendering of a base paper or there is known a specific paper-making method such as paper-making with a paper machine having an upper dehydration mechanism, paper-making with a Fourdrinier two-layer paper machine or the bulk density increasing press of a wet paper. However, these methods are still insufficient for overcoming the above problems, and in particular, they are absolutely insufficient for improving the gloss appearance of an image material using a resin-coated paper as a support and a print thereon.
Meanwhile, the most simplest method for improving the smoothness of a resin-coated paper for glossy use is, generally, to increase the thickness of the front resin layer. However, as the thickness of the front resin layer is increased, particularly, when the above thickness is greater than 31 xcexcm, there is caused a problem that a resin-coated paper, an imaging material using the resin-coated paper as a support and its print curl toward an image-forming layer side and are much troublesome to handle, i.e., a problem that the curl resistance is degraded.
Further, a resin-coated paper is improved in smoothness by using a base paper having excellent smoothness as a base paper for the resin-coated paper. However, there is often involved a problem that an imaging material using the above resin-coated paper as a support and its print have a poor stiffness. When an imaging material, a photographic material in particular, has a poor stiffness, there is sometimes caused a problem that the developability, automatic developability in particular, is degraded. Further, a print is manually taken up for its appreciation, and a xe2x80x9cpanoramaxe2x80x9d having a large width has a problem that it is difficult to appreciate when it has a poor stiffness. An imaging material and its print are therefore required to have a strong stiffness, while, as a result of studies by the present inventors, it has been found that the stiffness of an imaging material and its print greatly depends upon the strength of stiffness of a resin-coated paper as a support and that the stiffness of the resin-coated paper greatly depends upon the strength of stiffness of a base paper. However, the problem of stiffness of a base paper often has a contradicting relationship with the smoothness of the base paper, and the following inconsistent problems have been found. When the smoothness is good, the stiffness is poor. When the stiffness is sufficient, the smoothness is poor, and as a consequence, the stiffness of an imaging material using the resin-coated paper as a support and its print is poor, or the gloss appearance of the print, a photographic print in particular, is poor.
There are some methods conventionally proposed for overcoming the above problems of a support for an imaging material of a resin-coated paper type. JP-A-61-132949 discloses a method for providing a photographic support of a resin-coated paper type having a high rigidity and a high gloss by a photographic base paper formed of a first coating film composed mainly of a low-density polyethylene and a second coating layer composed of a polymer having a high rigidity modulus. As a polymer having a higher rigidity modulus, the above publication discloses high-density polyethylene (HDPE), polypropylene (PP), polycarbonate (PC), linear low-density polyethylene (LLDPE), polyamides such as nylon 11, nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). However, the use of the above method is still insufficient for improving the gloss appearance of an imaging material using a resin-coated paper as a support and a print thereon, and there occurs a problem that the curl resistance is degraded. That is, the following problem occurs. When a polymer having a high density is used as a polymer in the second coating layer, and in particular, with an increase in the above density or with an increase in the content of the above polymer in the coating layer, a resin-coated paper, an imaging material using the resin-coated paper as a support and its print show poor curl resistance.
Further, JP-A-7-120868 discloses a method in which at least two water-resistant-resin-coated layers are formed and a water-resistant resin of a layer farthest from a base paper has a higher density than a water-resistant resin of any other layer(s), and JP-A-7-168308 discloses a method in which at least two water-resistant-resin-coated layers are formed and a resin having a specific flexural modulus is used as a water-resistant resin for an outer-most layer, for improving the adhesion between a base paper and the water-resistant resin layers and the property of peeling from a cooling roll, to provide a support for a photographic paper of a resin-coated paper type. However, the above methods are still insufficient for improving the gloss appearance of an imaging material using a resin-coated paper as a support and of a print thereon. Further, there occurs another problem that the resin-coated paper and an imaging material using the resin-coated paper as a support are degraded in curl resistance. That is, the following problem occurs. When a water-resistant resin having a high density is used as a water-resistant resin in a coating layer, and in particular, with an increase in the above density or with an increase in the content of the above water-resistant resin in the coating layer, a resin-coated paper, an imaging material using the resin-coated paper as a support and its print show poor curl resistance.
Under the circumstances, it is therefore an object of the present invention to provide a support for an imaging material, which support is formed of a paper substrate composed mainly of a natural pulp and a resin layer coated on the front surface of the paper substrate, which can give an imaging material and its print having a high gloss appearance and being free of gloss non-uniformity, and which is excellent in productivity and economic performance in that the support is improved in its peeling from a cooling roll used for its production so as not to cause any non-uniformity in gloss, that the curl resistance thereof is improved, that the support has strong stiffness and that the support can be stably produced at a high speed.
The present inventors have therefore made diligent studies to develop a support for an imaging material which support has the above desirable properties, and as a result, have found the following. A resin-coated-paper-based support for an imaging material, in which a resin sheet on a side where an image is to be formed and a base paper have a multi-layered structure each or a resin-coated-paper-based support for an imaging material in which a base paper has a multi-layered structure of a layer structure having a specific thickness and containing a broad-leaved tree pulp having a specific fiber length and a resin sheet on a side where an image is to be formed is a polyolefin resin sheet, can give an imaging material and a print having a high gloss appearance and being free of gloss non-uniformity, is improved in the property of peeling from a cooling roll so that no peel non-uniformity takes place, and can be stably produced in a high speed.
Further, it has been found that a support in which a resin sheet on a side where an image is to be formed has a multi-layered structure, a top layer thereof contains a specific amount of a polyethylene-based resin having a density equivalent to, or higher than, a specific value and has a specific thickness, a bottom layer thereof contains a polyethylene-based resin having a density less than a specific value, the content of the polyethylene-based resin being the largest in the bottom layer, and a paper substrate is composed mainly of a natural pulp having a specific fiber length, can give an imaging material and a print having a high gloss appearance, excellent curl resistance and a strong stiffness, and can be stably produced at a high speed.
The present invention has been made on the basis of the above findings.
That is, according to the present invention, there is provided a resin-coated-paper-based support for an imaging material which support comprises a base paper and a sheet of a resin having film formability coated at least on a side of the base paper where an image is to be formed, characterized in that the resin sheet on the side where an image is to be formed and the base paper have a multi-layered structure each (the above support for an imaging material will be sometimes referred to as xe2x80x9csupport I for an imaging materialxe2x80x9d hereinafter).
According to the present invention, further, there is provided a resin-coated-paper-based support for an imaging material which support comprises a base paper and a sheet of a resin having film formability coated at least on a side where an image is to be formed, characterized in that the base paper has a multi-layered structure, a paper layer adjacent to the polyolefin resin sheet on the side where an image is to be formed has a thickness equivalent to 10 to 40% of a thickness of the base paper as a whole and is composed of a broad-leaved tree craft pulp beaten to an average fiber length of 0.3 to 0.5 mm, and that, of the other layers of the base paper, a layer composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved tree craft pulp has a total thickness equivalent to, or greater than, 60% of the thickness of the base paper as a whole (the above support for an imaging material will be sometimes referred to as xe2x80x9csupport II for an imaging materialxe2x80x9d hereinafter).
Further, according to the present invention, there is provided a support for an image material, which is formed of a paper composed mainly of a natural pulp, as a substrate, and a multi-layered resin sheet coated on a surface of the paper substrate where an image-forming layer is to be formed, characterized in that an upper layer (surface layer) A in the multi-layered sheet contains at least 50% by weight of a polyethylene-based resin (a) having a density of at least 0.940 g/cm3 and has a thickness equivalent to, or smaller than, 50% of a thickness of the multi-layered resin sheet, that a lower layer (or each of lower layers present below the surface layer) B contains a largest amount of a polyethylene-based resin (b) having a density of less than 0.940 g/cm3 among polyethylene-based resins in the layer(s) B, and that the paper substrate is composed mainly of a natural pulp having an average fiber length of 0.45 to 0.65 mm (the above support for an imaging material will be sometimes referred to as xe2x80x9csupport III for an imaging materialxe2x80x9d hereinafter).
In the present invention, the xe2x80x9caverage fiber lengthxe2x80x9d of pulp refers to a length weighted mean fiber length (mm) obtained by measuring a beaten pulp according to JAPAN TAPPI Paper Pulp Testing Method No. 52-89, xe2x80x9cMethod of testing paper and pulp for fiber lengthxe2x80x9d.
In the support I for an imaging material, provided by the present invention, the base paper and the resin sheet on a side where an image is to be formed (front side) have a multi-layered structure each. In the support II for an imaging material, the resin sheet on the front side is a polyolefin resin sheet, the base paper has a multi-layered structure, and the layer structure is specifically constituted.
In the support I for an imaging material, provided by the present invention, it is not clear why the mere formation of the base paper and the resin sheet as multi-layered structures improves the gloss appearance. However, it is assumed that the following statistical properties work. When each of the base paper and the resin sheet is increased in thickness as a single layer, the fluctuation of the thickness increases with an increase in thickness, while the division of a layer into layers relatively lessens an increase in the fluctuation due to a phase deviation of the fluctuation and a difference in frequency. It is also assumed that a combination of the base paper and the resin sheet produces an effect not only for the above reason but also because the size of concave and convex shapes on a surface comes into the acute region of human eyes.
In the support I for an imaging material (to be sometimes simply referred to as xe2x80x9csupport Ixe2x80x9d hereinafter) and the support II for an imaging material (to be sometimes simply referred to as xe2x80x9csupport IIxe2x80x9d hereinafter) provided by the present invention, the multi-layered base paper can be formed by any one of a method in which a multi-layer-structured head box is used, a method in which pulp slurries for upper layers are consecutively fed onto a pulp slurry for a lower layer in the step of dehydration on a wire and a method in which layers made in the form of sheets with a Fourdrinier paper machine or a cylinder paper machine are combined. In view of an interlayer bonding strength, however, it is preferred to form the multi-layered base paper at an early stage of paper making.
In the support I of the present invention, a paper layer adjacent to the front resin sheet has a thickness, preferably, of at least 10 xcexcm, more preferably at least 30 xcexcm, particularly preferably at least 50 xcexcm and is composed of a natural pulp beaten to an average fiber length of 0.3 to 0.5 mm. In this case, a further favorable result can be produced. The pulp which forms layer(s) other than the above layer adjacent to the front resin sheet is preferably that which is beaten to an average fiber length in the range of from 0.5 to 0.8 mm. When the fiber length of the pulp in any one of the layer adjacent to the front resin sheet and the other layer(s) is too small, the internal bonding strength of the base paper may decrease or the stiffness thereof may decrease. When the pulp fiber length of the layer adjacent to the front resin sheet is too large and equivalent to the length of the pulp fiber length of the other layer(s), the effect of the present invention is limitative. On the other hand, when the pulp fiber length of the layers as a whole is too large, the practical commercial value of the support I decreases although the effect of the present invention is exhibited as compared with a case where the present invention is not practiced.
On the other hand, in the support II of the present invention, the paper layer adjacent to the polyolefin resin sheet on the front side has a thickness equivalent to 10 to 40%, preferably 20 to 30%, of the thickness of the base paper as a whole, and is composed of a broad-leaved tree craft pulp beaten to an average fiber length of 0.3 to 0.5 mm. Further, of the other layers of the base sheet, the layer composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved craft pulp is required to have a total thickness equivalent to, or greater than, 60% of the thickness of the base paper as a whole.
When the fiber length of the pulp in any one of the layer adjacent to the front resin sheet and the other layer(s) is too small, the internal bonding strength of the base paper may decrease or the stiffness thereof may decrease. When the pulp fiber length of the layer adjacent to the front resin sheet is too large and equivalent to the length of the pulp fiber length of the other layer(s), the effect of the present invention is limitative. On the other hand, when the pulp fiber length of the layers as a whole is too large, no sufficient gloss appearance can be obtained. When the layer adjacent to the front resin sheet is composed of a conifer pulp, or when the other layer(s) is composed of a large content of a conifer pulp, the outcome is that the gloss appearance is impaired. When the layer adjacent to the front resin sheet is composed of a broad-leaved sulfite pulp, or when the other layer(s) is composed of a large content of a broad-leaved sulfite pulp, the stiffness is insufficient. When the thickness of the layer which is composed of a desired composition and adjacent to the front resin sheet is less than 10% of the total thickness of the base paper as a whole, the gloss appearance is insufficient, and when the above thickness exceeds 40%, the stiffness is insufficient. When the total thickness of the layer composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved craft pulp is less than 60% of the total thickness of the base paper as a whole, some kinds of pulp used for compensating an amount deficiency may cause an insufficient stiffness or an insufficient gloss appearance.
Preferably, the above layer composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved craft pulp is a layer having a thickness equivalent to, or greater than, 60% of a paper layer as a whole, which paper layer continues from the paper surface on the side opposite to the side where an image is to be formed. More preferably, the above paper layer consists of two layers, a layer composed of a broad-leaved tree craft pulp beaten to an average fiber length of 0.3 to 0.5 mm and a layer composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved craft pulp. on the other hand, when the layer composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved craft pulp has other layer in an intermediate position thereof, and if the xe2x80x9cother layerxe2x80x9d is composed of a conifer pulp, the conifer pulp is disadvantageous for the gloss appearance. A broad-leaved tree sulfite pulp is also disadvantageous in view of stiffness. Similarly, when other layer is present between the layer composed of a broad-leaved tree craft pulp beaten to an average fiber length of 0.3 to 0.5 mm and the layer composed of a pulp composition which is beaten to an average fiber length of 0.5 to 0.8 mm and contains at least 80% by weight of a broad-leaved craft pulp, and if the xe2x80x9cother layerxe2x80x9d is composed of a conifer pulp, the conifer pulp is disadvantageous for the gloss appearance. A broad-leaved tree sulfite pulp is also disadvantageous in view of stiffness.
In the supports I and II of the present invention, the pulp is preferably beaten so as to have a freeness in the range of from 250 ml to 360 ml, more preferably beanten to have a freeness of from 280 ml to 330 ml. When the freeness of the pulp is too low, the pulp may show insufficient paper making suitability, or the base paper may have low stiffness. When the freeness of the pulp is too high, the base paper tends to have a poor formation. In the present invention, the xe2x80x9cfreenessxe2x80x9d refers to a freeness (ml) found by measuring a beaten pulp according to TAPPI Standard Pulp testing method No. T227m-58 xe2x80x9cFreeness of Pulpxe2x80x9d.
In the supports I and II of the present invention, the pulp having a fiber length and a freeness in desirable ranges can be can be obtained by optimizing a balance between the cutting-based beating and the beating in a viscous state. Specifically, the balance between the cutting-based beating and the beating in a viscous state can be optimized by beating the pulp under a series of combined experimental conditions with regard to beating conditions such as a ratio of the cutting-based beating and the beating in a viscous state, a beating time, a pulp concentration and a beating power and measuring a sampled pulp slurry for a pulp fiber length and a freeness of the pulp.
In the supports I and II of the present invention, the layer(s) of the base paper other than the paper layer adjacent to the front resin sheet is generally composed of a natural pulp, while the natural pulp may contain a synthetic fiber or a synthetic pulp so long as it does not hamper the performance of the base paper. The natural pulp is preferably selected from wood pulps such as broad-leaved tree bleached kraft pulp, broad-leaved tree bleached sulfite pulp, conifer bleached kraft pulp, conifer bleached sulfite pulp and broad-leaved tree/conifer mixed bleached sulfite pulp. Further, various pulps including non-wood pulp, soda pulp, dissolving pulp and others such as reclaimed pulp (recycled paper pulp) may be used. In the support I of the present invention, the layer(s) adjacent to the front resin sheet is preferably composed of a broad-leaved tree sulfite pulp or a broad-leaved tree kraft pulp. In the support II of the present invention, the layer(s) adjacent to the front resin sheet is essentially required to be composed of a broad-leaved tree kraft pulp.
In the supports I and II of the present invention, each layer of the base paper may contain various additives which are added when paper material slurries are prepared. The additives include sizing agents such as fatty acid metal salt, fatty acid, emulsified alkyl ketene dimer or epoxidized higher fatty acid amide disclosed in JP-B-62-7534, emulsified alkenyl- or alkylsuccinic acid anhydride and a rosin derivative, dry paper strength reinforcing agents such as anionic, cationic or amphoteric polyacrylamide, polyvinyl alcohol, cationic starch and plant-originated galactomannan, wet paper strength reinforcing agents such as a polyamine polyamide epichlorohyrin resin, fillers such as clay, kaolin, calcium carbonate and titanium oxide, fixing agents such as aluminum chloride and water-soluble aluminum salt including aluminum sulfate, pH adjusting agents such as sodium hydroxide, sodium carbonate and sulfuric acid and others such as colorant pigments, colorant dyes and fluorescent brighteners disclosed in JP-A-63-20425 and JP-A-1-266537. The above additives are advantageously used in combination as required.
In the supports I and II of the present invention, the base paper may be impregnated with a composition containing any one of a water-soluble polymer, hydrophilic colloid or latex, an antistatic agent and other additives such as a pigment and a pH adjusting agent, or the above composition may be applied to the base paper, by size press, tub size press, etc., or with a blade, an air knife, etc. The water-soluble polymer or the hydrophilic colloid includes a starch-based polymer, a polyvinyl-alcohol-based polymer, a gelatin-based polymer, a polyacrylamide-based polymer and a cellulose-based polymer. The emulsion or the latex includes a petroleum resin emulsion, an emulsion or latex composed of at least ethylene and acrylic acid (or methacrylic acid) disclosed in JP-A-55-4027 and JP-A-1-18053, and an emulsion or latex of a styrene-butadiene copolymer, a styrene-acrylate copolymer, a vinyl acetate-acrylate copolymer, an ethylene-vinyl acetate copolymer, a butadiene-methyl methacrylate copolymer or a carboxy-modified product of any one of these. The antistatic agent includes alkali metal salts such as sodium chloride and potassium chloride, alkaline earth metal salts such as calcium chloride and barium chloride, colloidal metal oxides such as colloidal silica and organic antistatic agents such as polystyrene sulfonate. The pigment includes clay, kaolin, calcium carbonate, talc, barium sulfate and titanium oxide. The pH adjusting agent includes hydrochloric acid, phosphoric acid, citric acid and sodium hydroxide. The above colorant pigment, colorant dye and fluorescent brightener may be also used. The above additives are advantageously used in combination as required.
In the supports I and II of the present invention, the base paper is made such that the layer thickness non-uniformity index Rpy in a paper-making direction to be defined below is preferably 250 mV or less, more preferably 200 mV or less, particularly preferably 150 mV or less. The term xe2x80x9clayer thickness non-uniformity indexxe2x80x9d refers to a value obtained by allowing a sample to run between two spherical tracers, scanning the sample in the paper-making direction of the sample after zero adjustment at a constant speed of 1.5 m/minute with a film thickness measuring apparatus which measures a thickness fluctuation of the sample as an electric signal through an electronic micrometer, under conditions where the sensitivity range of the electronic micrometer is xc2x115 xcexcm/xc2x13 V, to measure the sample for a thickness fluctuation in the paper-making direction, subjecting obtained measurement signal values to fast Fourier transform with an FFT analyzer using a hanning window as a time window, determining a power spectrum (unit: mV2) based on an addition mean of additions carried out 128 times, totalling power values in the frequency band of 2 Hz to 25 Hz, multiplying the total by ⅔ and raising the obtained product to xc2xd power.
For producing a base paper having a layer thickness non-uniformity index Rpy of 250 mV or less for the support I of the present invention, specifically, there is used at least 30% by weight, preferably at least 50% by weight, of a broad-leaved tree pulp which is properly beaten. For example, as a complete pulp for constituting the base paper, there is used a broad-leaved tree kraft pulp which is beaten to a fiber length of, preferably, 0.8 mm or less, more preferably 0.6 mm or less. The layer adjacent to the front resin sheet has a thickness of, preferably, at least 10 xcexcm, more preferably at least 30 xcexcm, particularly preferably at least 50 xcexcm. And, for the above layer adjacent to the front resin sheet, further preferred is a pulp which is beaten to a fiber length of 0.3 mm to 0.5 mm. The base paper is preferably produced by making paper from the slurry containing additive chemicals with a Fourdrinier paper machine according to a proper paper-making method such that a uniform formation can be obtained.
For producing a base paper having a layer thickness non-uniformity index Rpy of 250 mV or less for the support II of the present invention, specifically, there is used at least 80% by weight of a broad-leaved tree pulp which is properly beaten. For example, as a complete pulp for constituting the base paper, there is used a broad-leaved tree kraft pulp which is beaten to a fiber length of 0.8 mm or less, preferably 0.6 mm or less. For the layer which adjacent to the front resin sheet and has a thickness equivalent to 10 to 40%, preferably 20 to 30%, of the thickness of the base paper, the pulp is beaten to a fiber length of 0.3 mm to 0.5 mm. The base paper is preferably produced by making paper from the slurry containing additive chemicals with a Fourdrinier paper machine according to a proper paper-making method such that a uniform formation can be obtained.
The base paper for each of the supports I and II can be produced by a combination of proper paper-making techniques in which a Fourdrinier paper machine having a proper upper dehydration mechanism, which machine causes proper turbulence on a paper material slurry, is used, multi-stage wet press, preferably at least three-stage wet press, is applied to a wet part, a smoothing roll is provided at the final stage of a press part, such that a uniform formation can be obtained, and the obtained paper is calendered with a machine calender, a super calender or a hot calender to form a base paper having a layer thickness non-uniformity index of 250 mV or less.
In the supports I and II of the present invention, the central plane average roughness SRa of the front surface of the base paper measured in a paper-making direction with a stylus-applied three-dimensional surface roughness tester at a cut-off value of 0.8 mm (the central plane average roughness on the front surface of a base paper in a paper-making direction at a cut-off value of 0.8 mm, measured with a stylus-applied three-dimensional surface roughness tester, will be sometimes simply abbreviated as xe2x80x9ccentral plane average roughness SRaxe2x80x9d hereinafter) is advantageously 1.50 xcexcm or less, preferably 1.40 xcexcm or less, more preferably 1.45 xcexcm or less, most preferably 1.25 xcexcm or less. In the present specification, the central plane average roughness at a cut-off value of 0.8 mm, measured with a stylus-applied three-dimensional surface roughness tester, is defined by the expression 1.   SRa  =            1      Sa        ⁢                  ∫        0        WX            ⁢                        ∫          0          WY                ⁢                              "LeftBracketingBar"                          f              ⁡                              (                                  x                  ,                  y                                )                                      "RightBracketingBar"                    ⁢                      xe2x80x83                    ⁢                      ⅆ            x                    ⁢                      xe2x80x83                    ⁢                      ⅆ            y                              
wherein Wx is a length of a sample surface region in an X-axis direction (paper-making direction), Wy is a length of the sample surface region in a Y direction (direction at speed angles with the paper-making direction), and Sa is an area of sample surface region.
Specifically, a machine SE-3AK and a machine SPA-11 supplied by Kosaka Laboratories (Japan) are used as a stylus-applied three-dimensional surface roughness tester and a three-dimensional roughness analyzer, and the central plane average can be determined under conditions where the cut-off value is 0.8 mm, Wx=20 mm, Wy=8 mm and therefore, Sa=160 mm2. In data processing in the X-axis direction, sampling was carried out in 500 points, and scanning in the Y-axis direction is carried out in at least 17 lines.
The base paper having a central plane average roughness SRa of 1.50 xcexcm or less, which is preferably used for the supports I and II of the present invention, can be specifically produced as follows. While a wet paper is dried, the wet paper is subjected to multi-staged bulk density increasing press. Further, the produced base paper is calendered in at least two lines by means of a machine calender, a super calender or a hot calender. For example, in the first line, the base paper is treated with a machine calender or a hot machine calender or both, and in the second line and thereafter, the base paper is treated with a machine calender as required and treated with a hot soft calender as described in JP-A-4-110938. Preferably, the base paper is impregnated with a water-soluble polymer, a hydrophilic colloid or a polymer latex, or any one of these is applied to the base paper, in an amount of at least 1.0 g/m2, preferably at least 2.2 g/m2 by size press, tub size press, blade coating or air knife coating.
In the supports I and II of the present invention, the density of the base paper, excluding an ash content, is preferably 0.80 g/cm3 to 1.15 g/cm3, more preferably 0.85 g/cm3 to 1.05 g/cm3, while the above density shall not be limited thereto. The thickness of the base paper is not specially limited, while the basis weight of the base paper is advantageously 40 g/m2 to 250 g/m2, preferably 70 g/m2 to 220 g/m2.
In the supports I and II for an imaging material, provided by the present invention, the surface (front surface) of the base paper where an image-forming layer is to be formed is coated with a resin sheet containing a resin having film formability. The reverse surface of the base paper is preferably coated with a resin sheet containing a resin having film formability.
When the resin having film formability in the front resin sheet and the resin having a film formability in the reverse resin sheet are thermoplastic resin(s), the support I and II are produced by a so-called melt-extrusion coating method in which resin composition(s) for the front resin sheet and the reverse resin sheet is/are cast in the form of a film onto a running base paper through a slit die with a melt extruder to coat the base paper. Generally, the support is produced by a series of steps in which a molten resin composition is extruded in the form of a film onto a running base paper through a slit die with a melt extruder and cast to coat the base paper, the so-formed films and the base paper are bonded under pressure between a press roll and a cooling roll and the resultant laminate is peeled from the cooling roll.
The present inventors have found that the effect of the present invention can be greatly remarkably exhibited owing to synergistic effects produced by constituting the front resin sheet of the support I as a multi-layered structure and constituting the base paper as a multi-layered structure. That is, the following has been found. By constituting the front resin sheet of the support I for an imaging material in the present invention as a structure of two or more layers, an imaging material having the above support and its print can be remarkably improved in gloss appearance, the support is remarkably improved in the property of peeling from a cooling roll when produced, to prevent the occurrence of peel non-uniformity, and therefore the support for an imaging material can be stably produced at a high speed.
The support I for an imaging material, provided by the present invention, has a front resin sheet constituted of two or more layers, while the front resin layer constituted of two layers is preferred for effectively accomplishing the object of the present invention.
In the support II for an imaging material in the present invention, it is more advantageous to constitute the front resin sheet as a structure of two or more layers for improving the gloss appearance.
In the supports I and II, preferably, the front resin sheet constituted as a structure of two or more layers is produced by a melt extrusion coating method. The front resin sheet is produced by a so-called co-extrusion coating method in which two or more layers are concurrently extruded to coat the base paper, or by a so-called consecutive extrusion coating method in which a resin layer at least for the lowermost layer is first melt-extruded in one station and a resin layer at least for the uppermost layer is finally melt-extruded in another station. Otherwise, there may be employed a method in which the support which is being produced is once taken up and then allowed to pass a resin coating line a plurality of times. In the present invention, preferred is the support for an imaging material having a two-layered resin sheet produced by the consecutive extrusion coating method.
The slit die for the melt extrusion coating is preferably selected from a T-die, an L-die, a fish tail die or a flat die, and the diameter of the slit opening is preferably 0.1 mm to 2 mm. The die for the multi-layer extrusion may be any die of a feed block type, a multi-manifold type or a multi-slot type. Although differing depending upon the kind of a resin, the temperature of the molten film is generally preferably 280xc2x0 C. to 340xc2x0 C., and the temperature of a resin composition for the uppermost layer and the temperature of a resin composition for a resin layer positioned below it may be different. For example, when the temperature of the resin composition for the uppermost layer is set at a temperature 5 to 10xc2x0 C. lower than the temperature of the resin composition positioned below it, the resin layer is improved in the property of peeling from a cooling roll.
For the front resin sheet and the reverse resin sheet of the support I and the reverse resin sheet of the support II, the resin having film formability preferably includes thermoplastic resins such as a polyolefin resin, a polycarbonate resin, a polyester resin, a polyamide resin or a mixture of at least two of theses. In view of coatbility by melt extrusion, a polyolefin resin and a polyester resin are more preferred, and a polyethylene resin is particularly preferred. Further, the above resin may be selected from electron-beam-curable resins disclosed in JP-B-60-17104.
In the support II, a polyethylene resin is particularly preferred as a polyolefin resin used for forming the front resin sheet.
The above polyethylene resin includes a low-density polyethylene resin, an intermediate-density polyethylene resin, a high-density polyethylene resin, a linear low-density polyethylene resin, an ultra-low-density polyethylene resin, a copolymer of ethylene and xcex1-olefin such as propylene or butylene, a co-called carboxy-modified polyethylene resin which is a copolymer or a graft copolymer of ethylene and acrylic acid, ethyl acrylate or maleic anhydride, a polyethylene resin obtained by a high-pressure radical polymerization method using an autoclave reactor or a tubular reactor, a polyethylene resin produced by polymerization in the presence of a metallocene polymerization catalyst and a polyethylene resin produced by polymerization in the presence of a metal catalyst other than metallocene according to a Ziegler method or a Phillips method. These polyethylene resins may be used alone or in combination. The density, the melt flow rates (MFR, defined under JIS K 6760), the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while, advantageously, the resin component (or mixture of resins) for constituting the resin sheet has a density of 0.90 to 0.97 g/cm3, an MFR of 0.1 g/10 minutes to 50 g/10 minutes, preferably 0.3 g/10 minutes to 40 g/10 minutes.
The polyethylene resin produced by a high-pressure method, preferably used for the front resin layer of the support I or II includes various polyethylene resins having a long-chain branch, produced by a high-pressure method using an autoclave reactor or a tubular reactor. Examples of the above polyethylene resins produced by a high pressure method include a low-density polyethylene resin, an intermediate-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified ethylene resin. These polyethylene resins may be used alone or in combination. The density, MFR, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.90 to 0.95 g/cm3 and an MFR of 0.1 to 50 g/10 minutes, preferably 0.4 to 50 g/10 minutes.
The polyethylene resin produced by polymerization in the presence of a metallocene polymerization catalyst, particularly preferably used for the front resin layer of the support I or II, refers to a resin produced by polymerization in the presence of a polymerization catalyst which is increased in catalytic activity by combining a zirconium- or hafnium-containing metallocene with, preferably, methylaluminoxane as is disclosed in PCT Japanese Translation Publication 3-502710, JP-A-3-234718, PCT Japanese Translation Publication 63-501369, JP-A-3-234717 and JP-A-3-234718. Examples of the polyethylene resin produced by polymerization in the presence of a metallocene polymerization catalyst include an ultra-low-density polyethylene resin, a low-density polyethylene resin, an intermediate-density polyethylene resin, a high-density polyethylene resin, a linear low-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified polyethylene resin. These polyethylene resins may be used alone or in combination. The density, MFR, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.87 to 0.97 g/cm3 and an MFR of 0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.
The polyethylene resin produced by polymerization in the presence of a metal polymerization catalyst other than metallocene, particularly preferably used for the front resin layer of the support I or II, includes various polyethylene resins produced, e.g., by a Ziegler method or a Phillips method. The polyethylene resin produced by polymerization in the presence of a metal polymerization catalyst other than metallocene includes an ultra-low-density polyethylene resin, a low-density polyethylene resin, an intermediate-density polyethylene resin, a high-density polyethylene resin, a linear low-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified polyethylene resin. These polyethylene resins may be used alone or in combination. The density, MFR, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.87 to 0.97 g/cm3 and an MFR of 0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.
The polyester resin used for the front resin sheet and the reverse resin sheet of the support 1 and for the reverse resin sheet of the support II includes a polyethylene terephthalate resin, a polybutylene terephthalate resin, a polyester-based biodegradable resin, a mixture of at least two of these and a mixture of at least one of these with a polyethylene. resin. The density and the intrinsic viscosity [xcex7] of the polyester resin are not specially limited. As a specific example, a polyester resin (trade name xe2x80x9cNOVAPEX HS004xe2x80x9d supplied by Mitsubishi Chemical Co., Ltd., melting point 235xc2x0 C., density 1.33 g/cm3, intrinsic viscosity [xcex7] 0.73 dl/g) is available. Further, a mixture of a polyester resin with a polyethylene resin can be advantageously used. For example, a mixture (melting point 224xc2x0 C., supplied by Mitsubishi Chemical Co., Ltd.) of a polyethylene terephthalate copolymer resin with a polyethylene copolymer resin (melting point 74xc2x0 C.) graft-modified with maleic acid is available.
The polycarbonate resin used for the front resin sheet and the reverse resin sheet of the support I and the reverse resin sheet of the support II includes polycarbonate resins of various grades. Specifically, a polycarbonate resin (trade name: NOVAREX 7022A, density 1.20 g/cm3, MFR 12 to 16 g/10 minutes, softening point 160xc2x0 C. to 190xc2x0 C.) supplied by Mitsubishi Chemical Co., Ltd. is available.
As a polyethylene resin for the reverse side sheet of the support I or II of the present invention, preferred is a compounded resin composition prepared by pre-melting and pre-mixing 90 to 65 parts by weight of a high-density polyethylene resin having an MFR of 10 g/10 minutes to 40 g/10 minutes, preferably 10 g/10 minutes to 30 g/10 minutes, and a density of at least 0.960 g/cm3 and 10 to 35 parts by weight of a low-density or intermediate-density polyethylene resin having an MFR of 0.2 g/10 minutes to 3 g/10 minutes, preferably 0.2 g/10 minutes to 1.5 g/10 minutes and a density of 0.935 g/cm3 or less. Concerning the molecular weight distribution of the low-density or intermediate-density polyethylene resin, preferably, the percentage of a polyethylene resin having a molecular weight of at least 500,000 is preferably at least 10% by weight, particularly preferably at least 12% by weight. When the percentage of a polyethylene resin having a molecular weight of at least 500,000 is less than 10% by weight, undesirably, the shapability is poor and in particular, xe2x80x9cneck-inxe2x80x9d is heavy. The above molecular weight is measured by a GPC method using 150-C supplied by Waters Co., Ltd. (columns: GMH-XL HT 8 mmxcfx86xc3x9730 cmxc3x973 columns, supplied by Tosoh Corp., solvent: 1,2,4-trichlorobenzene, temperature 135xc2x0 C., flow speed: 1 ml/min.)
As a polyethylene resin for the reverse resin sheet of the support I or II of the present invention, preferred is a pre-melted and pre-mixed compounded resin. The compounded resin is prepared by melting and mixing the low-density or intermediate-density polyethylene resin and the high-density polyethylene resin in advance according to a simple melt-mixing method or a multi-stage melt-mixing method. For example, there is advantageously employed a method in which predetermined amounts of the low-density or intermediate-density polyethylene and the high-density polyethylene are melted and mixed optionally together with an antioxidant, a lubricant and the like with an extruder, a twin-screw extruder, a hot roll kneader, a Banbury mixer or a pressure kneader and the resultant mixture is pelletized.
In the supports I and II of the present invention, the uppermost resin layer (to be sometimes abbreviated as xe2x80x9cupper most layerxe2x80x9d hereinafter) of the front resin sheet and a resin layer under it (to be sometimes abbreviated as xe2x80x9cunder resin layerxe2x80x9d hereinafter) may have the same properties and the same composition or may have different properties and different compositions. The polyethylene resin for the uppermost layer and the polyethylene resin for the under resin layer can be selected from those polyethylene resins having the above density, MFR and molecular weight values and the above molecular weight distributions, and these resins may be used alone or in combination for each layer. When used in combination, those resins used may have the same properties or they may have different properties.
For example, the MFR of a polyethylene resin (including a mixture of at least two polyethylene resins) used for the uppermost layer may be higher or lower than, or the same as, the MFR of a polyethylene resin (including a mixture of at least two polyethylene resins, used in this sense hereinafter) used for the under resin layer. For example, a polyethylene resin having an MFR of 5 g/10 minutes to 20 g/10 minutes for the uppermost layer and a polyethylene resin having an MFR of 2 g/10 minutes to 10 g/10 minutes for the under resin layer may be used. Further, a polyethylene resin having an MFR of 2 g/10 minutes to 10 g/10 minutes for the uppermost layer and a polyethylene resin having an MFR of 5 g/10 minutes to 20 g/10 minutes for the under resin layer may be used. Further, polyethylene resin(s) having the same MFR values may be used for the uppermost layer and the lower resin layer.
Further, the density of a polyethylene resin (including a mixture of at least two polyethylene resins) used for the uppermost layer may be higher or lower than, or the same as, the density of a polyethylene resin (including a mixture of at least two polyethylene resins, used in this sense hereinafter) used for the under resin layer. For example, a polyethylene resin having a density of 0.925 g/cm3 to 0.970 g/cm3 for the uppermost layer and a polyethylene resin having a density of 0.870 g/cm3 to 0.925 g/cm3 for the under resin layer may be used. Further, a polyethylene resin having a density of 0.870 g/cm3 to 0.925 g/cm3 for the uppermost layer and a polyethylene resin having a density of 0.925 g/cm3 to 0.970 g/cm3 for the under resin layer may be used. Further, polyethylene resin(s) having the same density values may be used for the uppermost layer and the lower resin layer.
Further, at least one polyethylene resin whose melting point is higher or lower than, or the same as, the melting point of a polyethylene resin used for the under resin layer may be used for the uppermost layer. For example, a polyethylene resin having a melting point of at least 115xc2x0 C. for the uppermost layer and a polyethylene resin having a melting point of less than 115xc2x0 C. for the under resin layer may be used. Further, a polyethylene resin having a melting point of less than 115xc2x0 C. for the uppermost layer and a polyethylene resin having a melting point of at least 115xc2x0 C. for the under resin layer may be used. Further, polyethylene resin(s) having the same melting points may be used for the uppermost layer and the lower resin layer.
In view of the effects of the present invention, i.e., the achievements of remarkable effects on improvements in the gloss appearance of an imaging material and a print thereon and the property of peeling of the support, the following multi-layered front resin sheet of the supports I or II of the present invention is particularly preferred. That is, the front resin sheet has the uppermost layer composed of at least one polyethylene resin having a higher density than a polyethylene resin for the lower resin layer, at least one polyethylene resin having a higher melting point than a polyethylene resin for the lower resin layer, or at least one polyethylene resin having a higher density and a higher melting point than a polyethylene resin for the lower resin layer.
The front resin sheet of the support I or II of the present invention and the optionally provided reverse resin sheet of the support I or II may contain various additives. For improving the whiteness of the support and the sharpness of an image, it is preferred to incorporate a titanium dioxide pigment disclosed in JP-B-60-3430, JP-B-63-11655, JP-B-1-38291, JP-B-1-38292 and JP-A-1-105245. In addition to the titanium dioxide pigment, the front resin sheet and the reverse resin sheet may contain a white pigment such as zinc oxide, talc or calcium carbonate, a fatty acid amide such as stearic acid amide or arachic acid amide as a releasing agent, a fatty acid metal salt such as zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, zinc palmitate, zinc myristate or calcium palmitate as a dispersing agent for a pigment and a releasing agent, an antioxidant such as hindered phenol, hindered amine, phosphorus-containing antioxidant or a sulfur-containing antioxidant disclosed in JP-A-1-105245, a blue pigment or dye such as Cobalt Blue, Ultramarine, Cerulein Blue or Phthalocyanine Blue, a magenta pigment or dye such as Cobalt Violet, Phosphite Violet or Manganese Violet, a fluorescent brightener disclosed in JP-A-2-254440, and an ultraviolet absorbent. The above additives are properly combined and incorporated. Preferably, these additives are incorporated as a master batch or a compound. In view of effective improvements in the sharpness or whiteness of a print and the heat resistance, light resistance and peeling properties of the support for an imaging material, it is preferred to incorporate higher concentrations of a white pigment such as titanium oxide and other additives such as a fluorescent brightener, a colorant pigment, a colorant dye, an antioxidant, an ultraviolet absorbent and a releasing agent into the uppermost layer than to the under resin layer.
In the supports I and II of the present invention, preferably, the base paper is subjected to activation treatment such as corona discharge treatment or flaming treatment before the base paper is coated with compositions for the front and reverse resin sheets. Further, as described in JP-B-61-42254, an ozone-containing gas may be blown to a molten resin composition which is to be brought into contact with the base paper, before the running base paper is coated with the resin layer. The front and reverse resin sheets are respectively coated on the base paper preferably by continuous extrusion, a so-called tandem extrusion coating method. Further, the reverse resin sheet may be a multi-layered coating having at least two layers as well. The front resin sheet of the support for an imaging material may be treated so as to have a gloss surface, a finely roughened surface disclosed in JP-B-62-19732, a matted surface or a meshed surface, and preferably, the reverse resin sheet is generally treated so as to have a gloss-free surface.
In each of the supports I and II of the present invention, the thickness of the entire front resin sheet is advantageously 8 to 100 xcexcm, preferably 12 to 60 xcexcm, particularly preferably 18 to 40 xcexcm. Although not specially limited, the thickness of the lowermost layer of the front resin sheet of the support I and the thickness of the lowermost resin layer of the front resin layer of the support II when the front resin layer has a multi-layered structure, are preferably at least 25%, more preferably at least 39%, particularly preferably at least 50%, of the front resin sheet, in view of the effect on improvement in the gloss appearance of an imaging material and a print thereon. The reverse surface of the base paper is preferably coated with the reverse resin sheet composed mainly of a resin having film formability. The above resin is preferably a polyethylene resin. The thickness of the reverse resin sheet is preferably well-balanced with the thickness of the front resin sheet concerning curl resistance. The thickness of the reverse resin sheet is advantageously 8 to 100 xcexcm, preferably 12 to 60 xcexcm.
The support III for an imaging material (to be sometimes referred to as xe2x80x9csupport IIIxe2x80x9d hereinafter), provided by the present invention, will be explained below.
In the support II of the present invention, the front resin sheet is a multi-layered resin sheet composed of an upper layer (surface layer) A and a lower layer (B) (which refers to one layer or layers present under the surface layer). The upper layer (A) is required to contain at least 50% by weight of a polyethylene resin (a) having a density of at least 0.940 g/cm3. When the content of the polyethylene resin (a) is less than 50% by weight, there is no sufficient effect on the improvement of the gloss appearance of the imaging material and a print thereon. In view of the effect on the above improvement, the above content is preferably at least 60% by weight, particularly preferably at least 70% by weight. Further, when the density of the polyethylene resin (a) is less than 0.940 g/cm3, there is no sufficient effect on the improvement of the gloss appearance of the imaging material and a print thereon. In view of the effect on the above improvement, the above density is preferably at least 0.945 g/cm3, particularly preferably at least 0.950 g/cm3.
The above polyethylene resin (a) can be selected from various polyethylene resins, and polyethylene resins having various density values, melt flow rates, molecular weights and molecular weight distributions may be used alone or in combination. When a mixture of polyethylene resins is used, it is sufficient that the mixture should have a density (calculated density) of at least 0.940 g/cm3.
The thickness of the layer (A) is required to be equivalent to, or smaller than, the thickness of the multi-layered resin sheet. When the above thickness exceeds 50%, the effects of the present invention are not sufficiently exhibited. In view of the effects, the thickness of the layer (A) is preferably equivalent to, or smaller than, 35%, particularly preferably 20%, of the thickness of the multi-layered resin sheet.
In the front multi-layered resin sheet of the support III of the present invention, the polyethylene resin having a density of at least 0.94 g/cm3, contained in the upper layer (A), includes a polyethylene resin produced in the presence of a metallocene polymerization catalyst, a polyethylene resin produced in the presence of a metal catalyst other than the metallocene polymerization catalyst and a mixture of them.
The polyethylene resin produced by polymerization in the presence of a metallocene polymerization catalyst refers to a resin produced by polymerization in the presence of a polymerization catalyst which is increased in catalytic activity by combining a zirconium- or hafnium-containing metallocene with, preferably, methylaluminoxane as is disclosed in PCT Japanese Translation Publication 3-502710, JP-A-60-356, PCT Japanese Translation Publication 63-501369, JP-A-3-234717 and JP-A-3-234718. Examples of the polyethylene resin produced by polymerization in the presence of the above metallocene polymerization catalyst include an intermediate-density polyethylene resin, a high-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified polyethylene resin. These polyethylene resins may be used alone or in combination. The density, the melt flow rate, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.94 to 0.97 g/cm3, preferably 0.950 to 0.970 g/cm3, particularly preferably 0.960 to 0.970 g/cm3 and a melt flow rate of 0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.
The polyethylene resin produced by polymerization in the presence of a metal polymerization catalyst other than metallocene, particularly preferably used for the above front resin layer (A), includes various polyethylene resins produced, e.g., by a Ziegler method or a Phllips method. The polyethylene resin produced by polymerization in the presence of a metal polymerization catalyst other than metallocene includes an intermediate-density polyethylene resin, a high-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified polyethylene resin. These polyethylene resins may be used alone or in combination. The density, the melt flow rate, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.94 to 0.97 g/cm3, preferably 0.950 to 0.970 g/cm3, particularly preferably 0.960 to 0.970 g/cm3 and a melt flow rate of 0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.
In the support III of the present invention, for improving the curl resistance of the imaging material and its print and the shapability of the resin composition for the upper layer (A), it is preferred to use the above polyethylene resin having a density of at least 0.940 g/cm3 and a polyethylene resin (to be described later) having a density of less than 0.940 g/cm3, preferably a density equivalent to, or smaller than, 0.928 g/cm3, more preferably a density equivalent to, or smaller than, 0.924 g/cm3, particularly preferably a density equivalent to, or smaller than, 0.918 g/cm3. The term xe2x80x9cshapabilityxe2x80x9d in the present specification refers to overall shapability including the degree of xe2x80x9cneck-inxe2x80x9d, film breakage depending upon the degree of drawdown, the unstableness of flow caused by surging or draw resonance, the degree of occurrence of streaks on a molten resin film and the degree of occurrence of xe2x80x9cfoulingxe2x80x9d in a die lip.
The lower layer (B) of the multi-layered resin sheet is required to contain a largest amount of a polyethylene resin (b) having a density of less than 0.940 g/cm3 among polyethylene-based resins in the layer (B). When the density of the above polyethylene resin (b) is 0.940 g/cm3 or greater, there is no sufficient effect on the improvement in curl resistance. In view of the effect on the above improvement, the above density is preferably 0.928 g/cm3 or lower, more preferably 0.924 g/cm3 or lower, particularly preferably 0.921 g/cm3.
The above polyethylene resin (b) can be selected from various polyethylene resins, and the melt flow rate, the molecular weight and the molecular weight distributions of the polyethylene resin (b) are not specially limited. Various polyethylene resins may be used alone or in combination. When a mixture of polyethylene resins is used, it is sufficient that the mixture should have a density (calculated density) of less than 0.940 g/cm3.
The polyethylene resin having a density of less than 0.940 g/cm3, used for the lower layer (B), includes a polyethylene resin produced by a high-pressure method, a polyethylene resin produced by polymerization in the presence of a metallocene polymerization catalyst, a polyethylene resin produced by polymerization in the presence of a metal catalyst other than metallocene and a mixture of at least two of these.
The above polyethylene resin having a density of less than 0.940 g/cm3 for the lower layer (B), produced by a high-pressure method, includes various polyethylene resins having a long-chain branch, produced by a high-pressure method using an autoclave reactor or a tubular reactor. Examples of the polyethylene resins produced by a high-pressure method include a low-density polyethylene resin, an intermediate-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified polyethylene resin. These polyethylene resins may be used alone or in combination. The melt flow rate, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.90 to less than 0.94 g/cm3, preferably 0.90 to 0.928 g/cm3, more preferably 0.90 to 0.924 g/cm3, particularly preferably 0.90 to 0.921 g/cm3 and a melt flow rate of 0.1 to 50 g/10 minutes, preferably 0.4 to 50 g/10 minutes.
The polyethylene resin having a density of less than 0.940 g/cm3 for the lower layer (B), produced by polymerization in the presence of a metallocene polymerization catalyst is a resin produced by polymerization in the presence of a polymerization catalyst which is increased in catalytic activity by combining a zirconium- or hafnium-containing metallocene with, preferably, methylaluminoxane as is disclosed in PCT Japanese Translation Publication 3-502710, JP-A-60-356, PCT Japanese Translation Publication 63-501369, JP-A-3-234717 and JP-A-3-234718. Examples of the polyethylene resin produced by polymerization in the presence of the above metallocene polymerization catalyst include an ultra-low-density polyethylene resin, a low-density polyethylene resin, an intermediate-density polyethylene resin, a linear low-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified polyethylene resin. These polyethylene resins may be used alone or in combination. The density, the melt flow rates, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.87 to less than 0.94 g/cm3, preferably 0.870 to 0.928 g/cm3, more preferably 0.870 to 0.924 g/cm3, particularly preferably 0.870 to 0.921 g/cm3 and a melt flow rates of 0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.
The polyethylene resin having a density of less than 0.940 g/cm3 for the lower layer (B), produced by polymerization in the presence of a metal polymerization catalyst other than a metallocene polymerization catalyst includes various polyethylene resins produced, e.g., by a Ziegler method or a Phllips method. The polyethylene resin produced by polymerization in the presence of a metal polymerization catalyst other than metallocene includes an ultra-low-density polyethylene resin, a low-density polyethylene resin, an intermediate-density polyethylene resin, a linear low-density polyethylene resin, a copolymer of ethylene as a main component and an xcex1-olefin such as propylene or butylene and a carboxy-modified polyethylene resin. These polyethylene resins may be used alone or in combination. The density, the melt flow rate, the molecular weight and the molecular weight distribution of the polyethylene resin are not specially limited, while the polyethylene resin generally has a density of 0.87 to less than 0.94 g/cm3, preferably 0.870 to 0.928 g/cm3, more preferably 0.870 to 0.924 g/cm3, particularly preferably 0.870 to 0.921 g/cm3 and a melt flow rate of 0.05 to 500 g/10 minutes, preferably 0.08 to 300 g/10 minutes.
When at least two polyethylene resins having different melt flow rates are used in combination for the upper layer or the lower layer of the multi-layered sheet of the support III, it is preferred to use these polyethylene resins as a compounded resin composition prepared by melting and mixing them in advance. For example, when a polyethylene resin having a melt flow rate of 5 to 40 g/10 minutes and a polyethylene resin having a melt flow rate of 0.2 to 4.5 g/10 minutes are used in combination, it is preferred to use these polyethylene resins as a pre-melted and pre-mixed compounded resin composition. The so-prepared compounded resin composition is preferred in view of shapability, film uniformity and the prevention of clotting of a non-uniform resin called a resin gel. The compounded resin composition can be prepared by various methods, for example, a method in which at least two polyethylene resins are melted and mixed optionally together with other thermoplastic resin and additives such as an antioxidant, a lubricant and the like with a kneading extruder, a hot roll mill, a Banbury mixer or a pressure kneader and the resultant mixture is pelletized.
Although not specially limited, the melt flow rate of the polyethylene resin components as a total in the resin composition for the upper layer (A) or the lower layer (B) of the multi-layered resin sheet is preferably 2 to 20 g/10 minutes, more preferably 3 to 15 g/10 minutes in view of the melt extrusion coatability of the resin composition, shapability and the effect on the improvement in gloss appearance.
The reverse surface of the support III of the present invention is preferably coated with a resin sheet (C) containing a resin (c) having film formability. The resin (c) is preferably selected from thermoplastic resins such as a polyolefin resin, a polycarbonate resin and a polyamide resin. Of these, in view of melt extrusion coatability, a polyolefin resin is more preferred, and a polyethylene resin is particularly preferred. Further, an electron-beam-curable resin disclosed in JP-B-60-17104 may be also used.
The polyethylene resin preferred for the reverse resin sheet of the support III is preferably a compounded resin composition which is prepared by pre-melting and pre-mixing 90 to 65 parts by weight of a high-density polyethylene resin having a melt flow rate of 10 g/10 minutes to 40 g/10 minutes and a density of at least 0.960 g/cm3 and 10 to 35 parts by weight of an low-density or intermediate polyethylene resin having a melt flow rate of 0.2 g/10 minutes to 3 g/10 minutes and a density of at least 0.935 g/cm3 or less.
As already described, the front multi-layered resin sheet of the support III has a structure of at least two layers, the upper layer (A) containing at least 50% by weight of the polyethylene resin (a) and the lower layer (B) containing a largest amount of the polyethylene resin (b).
The xe2x80x9cupperxe2x80x9d and xe2x80x9clowerxe2x80x9d in the present invention shows a relative-positional relationship in which the upper layer (A) is far from the base paper and the lower layer (B) is close to the base paper. In the constitution of the support III of the present invention, in view of the effects of the present invention, preferably, the upper layer is the uppermost layer, and the lower layer is the lowermost layer, and more preferably, the lower layer (B) constitutes an intermediate layer and the lowermost layer.
The resin layer of the upper layer (A) or the lower layer (B) may contain other resin (other than the resins (a) and (b)), e.g., a homopolymer such as a polyethylene resin, polybutene or a polypentene, a copolymer of at least two xcex1-olefins such as an ethylene-butylene copolymer or a polyester resin so long as the effects of the present invention are not impared and so long as the requirements of the present invention are satisfied.
The front resin sheet of the support III of the present invention may have a multi-layered structure of two layers or more, while, for efficiently achieving the object of the present invention, a two-layered or three-layered structure is preferred, and a three-layered structure of the uppermost layer, an intermediate layer and the lowermost layer is particularly preferred. The support III of the present invention is produced by a so-called melt extrusion coating method in which a resin composition molten under heat is cast onto a running base paper to coat it. For the above production, there may be employed a so-called co-extrusion coating method in which two or more resin layers for the support III are formed by concurrent-extrusion coating, or there may be employed a so-called consecutive extrusion coating method in which a resin layer for the lowermost layer is formed by melt extrusion coating in one station and then at least a resin layer for the uppermost layer is formed by melt extrusion coating in another station. In the present invention, when the front resin sheet has a structure of at least three layers, in view of the effect on improvement in gloss appearance of the imaging material and a print thereon, preferred is a support produced by a consecutive extrusion coating method in which at least resin layer for the lowermost layer is formed by melt extrusion coating, and then resin layers for the intermediate layer and the uppermost layer are formed by concurrent extrusion with another two-layer co-extruder. Further, when the consecutive extrusion coating is carried out, the resin layer for at least the lowermost layer may be subjected to activation treatment such as corona discharge treatment.
The slit die used for the melt extrusion coating is preferably selected from a T-die, an L-die, a fish tail die or a flat die, and the diameter of the slit opening is preferably 0.1 mm to 2 mm. The die for the multi-layer co-extrusion may be any die of a feed block type, a multi-manifold type or a multi-slot type. The temperature of the molten film is preferably 270xc2x0 C. to 340xc2x0 C., and the temperature of a resin composition for the uppermost layer and the temperature of a resin composition for a resin layer positioned under it may be different. For example, when the temperature of the resin composition for the uppermost layer is set at a temperature 5 to 20xc2x0 C. lower than the temperature of the resin composition for a resin layer under it, the resin layer is improved in the property of peeling from a cooling roll.
In the support III of the present invention, the total thickness of the front resin sheet composed of at least two layers is advantageously 8 to 100 xcexcm, preferably 12 to 60 xcexcm, particularly preferably 18 to 40 xcexcm. Further, in view of the effects on the improvements in gloss appearance of the imaging material and a print thereon and the curl resistance, the thickness of the upper layer (A) is preferably 35% or less, particularly preferably 20% or less, of the thickness of the front multi-layered resin sheet, although it is not specially limited. Further, the reverse surface of the base paper is preferably coated with a reverse resin sheet (C) composed mainly of a resin (c) having film formability. The resin (c) is preferably a polyethylene resin. The thickness of the reverse resin sheet (C) is particularly preferably determined so as to be well-balanced with the thickness of the front resin sheet concerning curl resistance. The thickness of the reverse resin sheet (C) is generally advantageously 8 to 100 xcexcm, preferably 12 to 60 xcexcm.
In the support III of the present invention, it is preferred to subject the base paper to activation treatment such as corona discharge treatment or flaming treatment before the resin composition for the front and reverse resin sheets are coated on the base paper. Further, as described in JP-B-61-42254, an ozone-containing gas may be blown to a molten resin composition which is to be brought into contact with the base paper, before the running base paper is coated with the resin layer. The front and reverse resin sheets are respectively coated on the base paper preferably by continuous extrusion, a so-called tandem extrusion coating method. Further, the reverse resin sheet may be a multi-layered coating having at least two layers as well. The front resin sheet of the support III for an imaging material may be treated so as to have a mirror surface, a gloss surface or a finely roughened surface disclosed in JP-B-62-19732, and preferably, the reverse resin sheet is generally treated so as to have a gloss-free surface.
The front resin sheet and the optionally provided reverse resin sheet of the support III of the present invention may contain various additives. Examples of the additives include those specified with regard to the supports I and II.
The support III of the present invention uses a base paper composed mainly of a natural pulp. The fiber length of the above natural pulp which is beaten before chemicals for paper are added is 0.45 mm to 0.65 mm. In view of the effect on improvements in the gloss appearance of an imaging material and a print thereon and the strength of stiffness thereof, the above fiber length is preferably 0.48 mm to 0.62 mm, more preferably 0.50 mm to 0.59 mm, particularly preferably 0.53 mm to 0.59 mm. Specifically, a natural pulp having a fiber length in the above range can be prepared by selecting a proper pulp, beating the pulp with a beating machine having a proper structure under a series of combined experimental conditions with regard to beating conditions such as a beating time, a pulp concentration and a beating power and measuring a sampled pulp slurry for a pulp fiber length. Further, as a condition of beating the pulp, it is preferred to optimize the balance between the cutting-based beating and the beating in a viscous state, and the freeness of the beaten pulp is preferably 200 ml to 400 ml, more preferably 230 ml to 370 ml, particularly preferably 260 ml to 340 ml.
The base paper for the support III of the present invention is preferably a natural pulp paper composed mainly of a natural pulp. Further, the base paper may be a mixed paper composed of a natural pulp as a main component and a synthetic pulp or a synthetic pulp. As the natural pulp, it is preferred to use a properly selected natural pulp disclosed in JP-A-58-37642, JP-A-60-67940, JP-A-60-69649 and JP-A-61-35442. The natural pulp can be advantageously selected from a conifier pulp, a broad-leaved tree pulp and a mixture of a conifer pulp and broad-leaved tree pulp which are subjected to general bleaching treatment such as treatment with hydrochloric acid, hypochlorite or chlorine dioxide, alkali-extraction or -treatment and optional bleaching treatment with hydrogen peroxide or oxygen, or a combination of these treatments. Further, various pulps such as a kraft pulp, a sulfite pulp and a soda pulp may be used, while a broad-leaved tree bleached craft is advantageously used.
In the base paper composed mainly of a natural pulp, used for the support III of the present invention, various additives may be added to a paper material slurry when the slurry is prepared. Examples of these additives include those specified with regard to the supports I and II.
Further, the base paper composed mainly of a natural pulp, used for the support III of the present invention, may be impregnated or coated with a composition containing any one of a water-soluble polymer, a hydrophilic colloid and a latex, an antistatic agent and other additive by size press, tub size press or coating such as blade coating or air knife coating. Examples of components of the above composition include those specified with regard to the supports I and II.
The thickness of the base paper for the support III is not specially limited, while the basis weight of the base paper is preferably 30 g/m2 to 250 g/m2, and the basis weight of the base paper for a photographic print is more preferably 70 g/m2 to 220 g/m2, particularly preferably 150 g/m2 to 200 g/m2.
In the base paper composed mainly of a natural pulp for the support III of the present invention, the central plane average roughness SRa of the front surface of the base paper measured in a paper-making direction with a stylus-applied three-dimensional surface roughness tester at a cut-off value of 0.8 mm is preferably 1.5 xcexcm or less, more preferably 1.4 xcexcm or less, particularly preferably 1.3 xcexcm or less.
According to studies by the present inventors, specifically, it has been found that the base paper having a central plane average roughness SRa of 1.5 xcexcm or less can be obtained by the following method, preferably by a combination of at least two methods below, more preferably by a combination of at least three methods below.
(1) As a natural pulp, it is preferred to use a broad-leaved tree bleached kraft pulp or a combination of a broad-leaved tree bleached kraft pulp and a broad-leaved tree bleached sulfite pulp. Further, there is used a natural pulp which is beaten so as to have an optimum fiber length and an optimum freeness as described above.
(2) During the drying of a wet paper, a bulk density increasing press is used. Specifically, a wet paper is subjected to a multi-stage bulk density increasing press as disclosed, for example, in JP-A-3-29945.
(3) Prior to forming an image-forming layer, the surface of the base paper where an image-forming layer is to be formed is coated with a layer formed of a coating composition containing a binder, preferably a water-soluble polymer, a hydrophilic colloid or a polymer latex. Specifically, the surface of the base paper where an image-forming layer is to be formed is coated with a coating composition containing a water-soluble polymer, a hydrophilic colloid or a polymer latex by size press, tub size press, blade coating or air knife coating to form a layer having a solid coating amount of at least 2 g/cm2, preferably at least 5 g/cm2. Further, the layer formed by the above coating preferably contains an inorganic or organic pigment for further improving the layer in flatness.
(4) The produced base paper is calendered in at least two lines by means of a machine calender, a super calender or a hot calender. Specifically, in the first line, the base paper is treated with a machine calender or a hot machine calender or both, and in the second line and thereafter, the base paper is treated with a machine calender, a hot calender or a hot soft calender as described in JP-A-4-110938. It is particularly preferred to treat the base paper with a combination of these. Further, the calender treatment in the second line and thereafter is preferably carried out on machine after the base paper is produced.
After the surface of the front resin sheet of any one of the supports I, II and III of the present invention is subjected to activation treatment such as corona discharge treatment or flaming treatment, an undercoat layer may be formed on the surface as disclosed in JP-A-61-84643, JP-A-1-92740, JP-A-1-102551 or JP-A-1-166035. Further, after the surface of the back resin sheet of any one of the supports I, II and III of the present invention is subjected to activation treatment such as corona discharge treatment or flaming treatment, a back coating layer may be formed on the surface for antistatic performance, and the like. The back coating layer may contain a proper combination of an inorganic antistatic agent, an organic antistatic agent, a hydrophilic binder, a latex, a curing agent, a pigment and a surfactant disclosed in JP-B-52-18020, JP-B-57-9059, JP-B-57-53940, JP-B-58-58859, JP-A-59-214849 and JP-A-58-184144.
Various photograph-constituting layers are formed on the supports I, II and III for imaging materials, provided by the present invention, and the supports I, II and III are used in a variety of fields including a photograph printing paper, a monochrome photograph printing paper, a photocomposition printing paper, a copy printing paper, a reversal photograph material, a negative or positive imaging material by a silver salt diffusion transfer method and a printing material. For example, an emulsion layer of a silver chloride, silver bromide, silver chlorobromide, silver iodide or silver cloroiodide may be formed thereon. A color coupler is contained in a silver halide emulsion layer to form a silver halide color photograph-constituting layers. A layer for constituting a photograph by a silver salt diffusion method may be formed thereon. As a binder for the above photograph-constituting layers, there may be used hydrophilic polymer materials such as polyvinyl pyrrolidone, polyvinyl alcohol, a sulfate ester compound of polysaccharide and the like, besides generally used gelatin. Further, the above photograph-constituting layers may contain various additives. Examples of the additive include sensitizing dyestuffs such as cyanine dyestuff and merocyanine dyestuff, chemically sensitizing agents such as a water-soluble gold compound and a sulfur compound, anti-fogging agents or stabiliers such as a hydroxy-trizaolopyrimidine compound and a mercapto-heteocyclic compound, film-curing agents such as formalin, a vinyl sulfone compound, an aziridine compound and an active halogen compound, application aids such as alkylbenzenesulfonate and sulfosuccinate, pollution preventers such as a dialkylhdyroquinone compound, a fluorescent brightener, a sharpness-improving dyestuff, an antistatic agent, a pH adjuster and a fogging agent. Further, water-soluble iridium and a water-soluble rhodium compound may be incorporated when silver halide is formed and dispersed.
A photographic material using the support I, II or III of the present invention can be subjected to treatments such as exposure, development, termination, fixing, bleaching and stabilization depending upon the photographic material as described in xe2x80x9cPhotographic Photosensitive Materials and Handling Methodxe2x80x9d (Syashin Gijutsu Koza 2, MIYAMOTO Goro, Kyoritsu Publishing Co. Japan). Further, a multi-layered silver halide color photographic material may be treated with a developer solution containing development promoters such as benzyl alcohol, thallium salt and phenidone, or it may be treated with a developer solution substantially containing no benzyl alcohol.
The supports I, II and III for imaging materials, provided by the present invention, on which various thermal transfer type heat transfer record receiving layers are formed, can be used as various thermal transfer type heat transfer record receiving materials. The synthetic resin which can be used for forming the above thermal transfer type heat transfer record receiving layers includes resins having an ester bond such as a polyester resin, a polyacrylate ester resin, a polycarbonate resin, a polyvinyl acetate resin, a polyvinyl butyral resin, a styrene acrylate resin and a vinyltoluene acrylate resin, resins having a urethane bond such as a polyurethane resin, resins having an amide bond such as a polyamide resin, resins having a urea bond such as a urea resin, and other resins such as a polycarprolactam resin, a styrene resin, a polyvinyl chloride resin, a vinyl chloride-vinyl acetate copolymer resin and a polyacrylonitrile resin. A mixture or a copolymer of these may be also used.
In the present invention, the above thermal transfer type heat transfer record receiving layer may also contain a releasing agent and a pigment in addition to the above resin(s). The releasing agent includes solid waxes such as polyethylene wax, amide wax and Teflon powder, a fluorine-containing or phosphate ester-containing surfactant and silicone oil. Of these releasing agents, silicone oil is the most preferred. The silicone oil may be in the form of an oil, while a curable silicone oil is preferred. The curable silicone oil includes reaction-curable, photo-curable and catalyst-curable silicone oils, while a reaction-curable silicone oil is the most preferred. The reaction-curable silicone oil includes amino-modified silicone oil and epoxy-modified silicone oil. The content of the above reaction-curable silicone oil in the receiving layer is preferably 0.1 to 20% by weight. The above pigment is preferably selected from extender pigments such as silica, calcium carbonate, titanium oxide and zinc oxide. The thickness of the receiving layer is preferably 0.5 to 20 xcexcm, more preferably 2 to 10 xcexcm.
The supports I, II and III for imaging materials, provided by the present invention, can be used as supports on which various ink receiving layers are formed. The ink receiving layer may contain a binder for improving the drying capability of an ink and for improving the sharpness (clearness) of an image. Specific examples of the binder include various gelatins such as lime-treated gelatin, acid-treated gelatin, enzyme-treated gelatin, a gelatin derivative, modified gelatin prepared by reacting gelatin with an anhydride of dibasic acid such as phthalic acid, maleic acid or fumaric acid, polyvinyl alcohols having various saponification degrees, carboxy-modified, cation-modified or amphoteric polyvinyl alcohol and a derivative thereof, starches such as oxidized starch, cationized starch, etherified startch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, synthetic polymers such as polyvinylpyrrolidone, polyvinylpyridium halide, sodium polyacrylate, acrylate-methacrylate copolymer salt, polyethyelene glycol, polypropylene glycol, polyvinyl ether, alkylvinyl ether-maleic anhydide copolymer, styrene-maleic anhydride copolymer and salt thereof and polyethyleneimine, conjugated diene copolymer latexes such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, vinyl acetate polymer latexes such as polyvinyl acetate, vinyl acetate-maleate copolymer, vinyl acetate-acrylate copolymer and ethylene-vinyl acetate copolymer, latexes of acrylate polymers or copolymers such as acrylate polymer, methacrylate polymer, ethylene-acrylate copolymer and styrene-acrylate copolymer, vinylidene chloride copolymer latexes, functional-group-modified polymer latexes prepared by modifying the above polymers with a monomer containing a functional group such as a carboxyl group, water-based adhesives including thermosetting synthetic resins as a melamine resin and a urea resin, synthetic resin adhesives such as polymethyl methacrylate, a polyurethane resin, an unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral and an alkyd resin, and inorganic binders such as alumina sol and silica sol disclosed in JP-A-3-24906, JP-A-3-281383 and Japanese Patent Application No. 4-240725. The above binders may be used alone or in combination.
The ink receiving layer of the inkjet recording material in the present invention may contain other additives in addition to the binder. Examples of the additives include surfactants including anionic surfactants such as long-chain alkylbenzenesulfonate and long-chain, preferably branched, alkylsulfosuccinate, nonionic surfactants such as polyalkylene oxide ether of lone-chain, preferably branched, alkyl group-containing phenol and polyalkylene oxide ether of long-chain alkyl alcohol and fluorinated surfactants disclosed in JP-B-47-9303 and U.S. Pat. No. 3,589,906, silane coupling agents such as xcex3-aminopropyltriethoxysilane and N-xcex2(aminoethyl) xcex3-aminopropyl trimethoxysilane, polymer curing agents such as an active halogen compound, a vinylsulfone compound, an aziridine compound, an epoxy compound, an acryloyl compound and an isocyanate compound, antiseptics such as p-hydroxybenzoate compounds disclosed in JP-A-1-102551, a benzthiazolone compound and an isothiazolone compound, colorant pigments disclosed in JP-A-63-204251 and JP-A-1-266537, colorant dyes, fluorescent brighteners, yellowing preventers such as sodium hydroxymethanesulfonate and sodium p-toluenesulfonate, ultraviolet absorbents such as a benzotriazole compound having a hydroxy-dialkylphenyl group on the 2-position, antioxidants such as poly-hindered-phenol compounds disclosed in JP-A-1-105245, handwritable materials such as organic or inorganic fine particles of starch powder, barium sulfate or silicon dioxide having a particle diameter of 0.2 to 5 xcexcm and organopolysiloxane compounds disclosed in JP-A-4-1337, pH adjusters such as sodium hydroxide, sodium carbonate, sulfuric acid, phosphoric acid and citric acid, octyl alcohol and a silicon-containing anti-foamer. The above additives are used in proper combination.
The supports for imaging materials, provided by the present invention, can provide imaging materials and prints thereon which have high gloss appearance and are free of non-uniformity in gloss. Further, the supports are improved in the properties of peeling from a cooling roll and are free from the occurrence of non-uniform peeling. Moreover, the supports have excellent curl resistance and strong stiffness, and the supports can be stably produced at a high speed and are therefore excellent in economic performance.